Our recent research has established that a system exists in human saliva which plays an important role in the maintenance, protection and repair of dental enamel. The key features of this system are the presence in saliva of, firstly, supersaturated but stabilized concentrations of calcium and phosphate ions, and secondly, two kinds of salivary macromolecules which stabilize the supersaturated saliva by inhibiting precipitation of calcium phosphate salts. The supersaturated saliva provides important protection for the teeth by providing driving forces which, firstly, stabilize the enamel mineral, secondly, oppose enamel dissolution and mineral transport during carious attack of the teeth, and, thirdly, provides a mechanism for the repair of many early carious lesions. The precipitation inhibitors control this supersaturation by, firstly, preventing precipitation of calcium phosphate salts in the salivary glands and the oral cavity, and secondly, because they inhibit crystal growth of calcium phosphate salts, they prevent unwanted accretion of mineral onto the tooth surface. Significantly, their mechanisms of action do not affect calcium and phosphate ion activities in the saliva. Also, it is probable that one or both of the inhibitors contribute to the formation of the acquired enamel pellicle, a protein integument present on the enamel surface which provides significant protection for the teeth. The purpose of the proposed research is to elucidate the mechanisms by which the precipitation inhibitors act, both in terms of their molecular structures, which are now partly known, and in terms of their post-secretion behavior in the oral cavity. In addition, we propose to establish their broad biological significance by studying species other than human, particularly sub-human primates and laboratory animals used for dental caries and periodontal disease research. From this research will come an improved understanding of important relationships which exist between the teeth and their oral environment, both in health and disease.